Heating of fluids



Feb. 15, 1938. M K 7 2,108,687

HEATING OF FLUIDS Filed Oct. 24, 1953 HEM 6' TUNNEL b/n/scr/ols ZOA/E.FIG. I

B T T I? ETTTTTTTTTTTT'TT'T INVENTOR EV MEKLER BY ORNEY been possible ina 4o ments located adjacent the roof of the Patented Feb. 15. 1938PATENT OFFICE HEATING OF FLUIDS Lev A. Mekler,

Oil Products Company, ration of Delaware This invention relates to animproved apparatus for the heating of fluids and more particularlyrefers to an improved form of furnace and heating method especiallyadapted for the heating' of hydrocarbon oils to the high temperaturesrequired for their pyrolytic conversion. By use of the combination offeatures provided by the present invention a greater flexibility ofoperating conditions is obtained than has heretofore simple furnacestructure of the general type disclosed. Flexibility of operation is anessential feature in cracking process furnaces, due to the widevariations and characteristics of different hydrocarbon oil crackingstocks. In the present invention this flexibility is attained in, asimple .furnace structure by a special arrangement of the fluid conduitand special flow of oil therethrough in combination with a method forcontrolling combustion,conditions in the furnace, particularly withrespect to the length, luminosity and other characteristics of the flameproduced.

One specific embodiment of the apparatus may, comprise a main furnacestructure having end walls, side walls, a roof and a floor, a combustionzone within said furnace, means forsupplying a, combustible fuel-airmixture to the combustion zone, means for separately supplyingcontrolled quantities of additional air to said combustion zone, aconvection heating zone located within the furnace and separated fromthe combustion zone by a bridge wall, means for removing-combustiongases from said furnace through the convection heating zone, a fluidconduit comprising a plurality of horizontal rows of serially connected,horizontally disposed tubular elements located within saidconvectionheating zone, a fluid conduit comprising a horizontal row ofserially connected, horizontally disposed tubular elefurnace,

a fluid conduit comprising a, horizontal row of seriallyconnected,horizontally disposed tubular elements located adjacent the floor of thecombustion zone, means for passing a fluid to be 45 heated, such ashydrocarbon oil, in a continuous stream, first through the fluidconduit-in the convection heating zone, then through the fluid conduitadjacent the-roof ofthe furnace, in a generaldirection counter-currentto the. direction of firing'and general direction of flow of thecombustion gases, and finally through the fluid conduit adjacent thefloor of the combustion zone in' a general direction concurrent to thedirection of firing and the general direction of flow of 55 thecombustion'gases.

' It for the purpose horizontally disposed tubular Chicago, 111.,assignor to Universal Chicago, 111., a corpo- Appli'cation October 24,1933, Serial No. 694,960 12 Claims. I (Cl. 122-356) The accompanyingdiagrammatic drawing 11- lustrates one form of apparatus embodying thefeatures of the present invention and the process of the presentinvention will be more apparent with reference to the followingdescription of 5 the drawing. Fig. 1 of the drawing is a crosssectionalside elevation of the furnace, and Fig.

'2 is a cross-sectional end elevation of the same furnace structureshown in Fig. 1.

The main furnace structure comprises side walls I and 2, end walls 3 and4, a robf 5 and a floor 6. Within the main furnace structure a bridgewall I separates combustion zone 8 from the convection heating zone 9.

One or preferably a plurality of similar firing 15 tunnels, one of whichis indicated at It in Fig.

1, are provided for the introduction of a combustible fuel-air mixtureinto combustion zone 8. Air ducts H and II are provided, in the caseillustrated, above and beneath firing tunnel of introducing additionalair 8 in controlled quantities regto combustion zone I2 and II. Fuel ofany suitulated by dampers able type such as oil, gas or pulverized solidfuel is supplied by means of any suitable type of bumerinot shown) tofiring tunnel Ill and a 25 of the air required for combustion is alsosupplied through tunnel It. When desired, a regulated portion of the airrequired for combustion, as well as any amount of excess air desired,may be supplied to combustion zone 8 through air ducts II and H and maybe proportioned, as desired, between the air ducts located,respectively, above and below firing tunnel Ill.

A fluid conduit 13 comprising, in the case here illustrated, a pluralityof horizontally disposed tubular elements l4 arranged in superimposed,horizontally parallel rows, is located within the convection heatingzone 9 and is supplied with 40 convection heat from the combustion gaseswhich pass from combustion zone 8, over bridge wall I, downward throughconvection zone 9 and. out of the furnace through flue l5 to a suitablestack (not shown).

Another fluid conduit l6 comprising, in the case here illustrated, asingle horizontal row of elements I4 is located adjacent the roof of thefurnace and is supplied with radiant heat from the flames and refractorywalls of the furnace as well as with convection heat from the hotcombustion gases. Another fluid conduit I'I, located along the floor ofthe combustion zone comprises, in the case illustrated, a singlehorizontal row of horizontally disposed tubular elements I 4 which aresupplied with radiant heat from the flames and hot refractory walls ofthe furnace, as well as, when desired, with convection heat (of variablemagnitude) from the hot combustion gases.

Also in the particular case here illustrated .a separate fluid conduiti8, similar in construction to fluid conduit I3, is located beneathfluid con- ,duit I3 in convection heating zone 9. Fluid con-' duit Itmay serve, for example, when the furnace is utilized for the conversionof hydrocarbon oils, as a steam generating or superheating coil or as ameans of reboiling reflux condensate from the fractionator of thecracking system or for any other desired purpose. It serves, in anycase, as a means of recovering additional heat from the furnace gases,prior to their passage through flue It to the stack but is neither anessential nor novel featureof the present invention.

In the preferred embodiment of the invention, adjacent tubes in each rowof fluid conduit I3 and the adjacent rows of this tube bank as well asadjacent tubes in each of the fluid conduits I6 and I! are connected inseries by means of return bends or headers I9 located at the ends of thetubes outside the heating zone, as indicated in Fig. 2 of the drawing.In Fig. 1 these return bend connections on the near ends of adjacenttubes are indicated by the lines I9. The tubes of fluid conduit I8 arealso connected in the same manner, in the particular case hereillustrated. I

In the preferred embodiment of the invention, particularly as applied tothe conversion'of hydrocarbon oils, the oil flows through tube banks orfluid conduits I3, I6 and IT in the order named although, when desired,the flow may be in sequence through banks I3, I1 and I6. Preferably, theoil passes through bank I3 in a general direction counter-current to thegeneral direction of travel of the combustion gases through this zoneand is then transferred, as indicated by line 20, to the tube of bank I6nearest end wall 4 of the furnace. The oil then passes through bank ISin a general direction counter-current to the general direction of theflow of the combustion gases and the direction of firing, passing fromthe end tube in bank I6 adjacent end wall 3 of the furnace, as indicatedby line 2|, to the tube at the same end of bank II. The oil passesthrough tube bank I! in a general direction concurrent to the generaldirection of firing and finally emerges from the end tube of bank I!nearest bridge wall I, from which it is discharged to subsequentportions of the cracking system (not shown).

It is within the scope of the invention, when desired, to eliminate thatportion of tube bank I6, indicated in the drawing as I6, which isimmediately above tube bank I3, in which case the oil is transferreddirectly from tube bank I3 to tube bank I6. When this arrangement isemployed a somewhat higher rate of heating will ordinarily be obtainedin tube bank I3, due to a somewhat higher combustion gas temperature inconvection heating zone 9 brought about by the elimination of thecooling surface indicated at I6. Also, a considerable quantity ofadditional radiant heat from the roof of the furnace will be impartedparticularly to the upper two or three rows of tubes in bank I3 and,when desired, section I6 of the fluid conduit may be replaced by one ormore additional rows of tubes at the top of bank I3.

The degree of combustion obtained in firing tunnel I I! is controlled bythe distribution of the air supplied to the furnace. When all of the airnecessary for combustion is supplied through tunnel Ill, together withthe fuel, all or the major portion of the combustion process will becompleted in the firing tunnel and only a relatively short flame willextend from the mouth of the tunnel into combustion zone 8. When thesame amount of total air is proportioned so that part of it is suppliedthrough air ducts I I, appreciable combustion of the fuel will beaccomplished in combustion zone 8 with a longer and more luminous flamein this zone. Variation in the quantity of excess air supplied to thefurnace, whether supplied through firing tunnel Ill or ducts II, servesto affect the furnace conditions in the usual manner. In this manner acontrol is obtained over the percentage of radiant heat, as compared tothe total heat imparted to the fluid undergoing treatment, as well asover the distribution of radiant heat to different portions of the fluidconduit.

By increasing the proportion of the air required for combustion suppliedthrough air ducts I I, the amount of combustion in combustion zone 8 isincreased and the proportion of radiant heat imparted to the fluidundergoing treatment may be increased. By firing with a greaterproportion of the air required for combustion supplied through thefiringtunnel III, a shorter semiluminousflame is obtained and the proportionof radiant heat is decreased with a corresponding increase in the amountof convection heat supplied to the tubes of the fluid conduit and to thefluid undergoing treatment.

When it is desired to increase the heat absorption in that portion ofthe fluid conduit located adjacent the floor of the furnace, a largeproportion of the secondary air used outside of tunnel I0 may besupplied through the air duct II, located above the firing tunnel. Therelatively cold air thus admitted above the firing tunnel, being heavierthan the products of combustion leaving tunnel I0, tends to blanket theflames and concentrate heat along the floor of the furnace. This is thereverse of the natural tendency of the flames and the heated gases torise rapidly, causing a concentration of heat along the roof of thefurnace, thereby supplying a large proportion of the total heat impartedto the oil as it passes through that portion of the fluid conduitlocated adjacent the roof of the furnace.

In the prese'ntinvention this natural tendency for the heattoconcentrate along the roof of the furnace may be augmented bysupplying a large portion of the secondary air required for combustionand, when desired, a regulated amount of excess air and/or steam,through the air duct II' located beneath firing tunnel II] so that thatportion of the fluid conduit located adjacent the floor of the furnacemay be utilized as what is commonly termed a soaking section, whereinthe fluid undergoing treatment may be maintained at or near thetemperature attained in the previous portion of the fluid conduitwithout the addition of any appreciable amount of sensible heat. This isparticularly desirable in the treatment of oils of a relatively lowboiling nature such as, for example, straight-run gasoline or othermotor fuel or motor fuel fractions of inferior anti-knock value,naphtha, kerosene or kerosene distillate, pressure distillate bottomsand the like.

On the other hand, it is ordinarily desirable, in the conversion of oilsof a relatively high boiltubes will only partially block the flow ofgases I ing nature such as residual oils, fuel oil, topped crude and insome cases intermediate oil such as gas oil and the like, to avoidmaintaining the oil at the maximum conversion temperature attained forany considerable length of time but to maintain a fairly constantincrease in temperature (rate of sensible heat input) throughout theentire path of travel of the oil through the fluid conduit. This isaccomplished in the present invention, in the manner previouslyindicated, by properly proportioning the total air required forcombustion between firing tunnel Ill and air ducts II and by regulationof the proportion of secondary air supplied, respectively, through theupper and lower air ducts ll.

As a further feature of the present invention additional means areprovided for controlling the heat input relationship between tube bankI'I, adjacent the floor of the furnace and tube bank l6 adjacent to theroof. This is accomplished by the installation or omission of a baiile22 between tube bank l1 and bridge wall I.

In the operation of a furnace, such as illustrated, the jet action ofthe stream of combustion gases from the firing tunnel creates a zone ofrelatively low pressure beneath the flame and the stream of hotcombustion gases near the point of exit of the gases from the firingtunnel, which, in the furnace shown, is in the zone occupied by aportion of tube bank I]. The inertia of the gases travelling towardbridge wall I produces, on the other hand a zone of relatively highpressure near the bridge wall. As a result there is a considerable flowof gases, countercurrent to the general direction of firing and the flowof the main body of the gases, from the bridge wall toward the firingtunnels between the tubes of bank I! and the floor of the fur-' nace anda considerable amount of convection heat is imparted to the. tubes ofbank H, which are sweptby this flow of gases, in addition to the radiantheat component supplied to the tubes of bank H from the flames, the mainbodyof gases and the hot refractories of the furnace. This materiallyincreases the overall rate of heat input in tube. bank of oil andfurnace temperatures indicate that an increasing rate of heat input isobtained from the inlet to the outlet of tube bank ll (i. e. from theportion of this bank'adjacent theflring tunnel to the portion adjacentthe bridge wall),

' because of this flow.

When the flow of gases beneath the floor tubes from the zone of highpressure to the zone of low pressure is either restricted or eliminatedthe furnace is operated by installing a baiile 22 between tube bank I!and bridge wail I whereby the convection component of heat input intobank H is reduced or completely eliminated. This results in a loweroverall rate of heat input to tube bank W and in or decreasing rateof.heat input from the inlet to the outlet of this bank.

The efiect of the baffle between tube bank it and bridge wall I may-bemodified to suit requirements. by altering the form or type of baffleemployed, for example, a solid baflle wall such as indicated in Figure 1of the drawing, extending from the floor of the furnace to above theupper surface of the floor tubes, will practically eliminate the flow ofgases-from the zone of high pressure adjacent the bridge wall to thezone of low pressure adjacent the firing tunnel. A perforated baflle ora bailie wall extending, for example, to only the lower surface of thefloor I I and careful measurements a substantially uniform from bridgewall I to the firing tunnels and by varying the size and spacing of theperforations and/or the height of the baflle wall the convection heatcomponent supplied to tube bank l1 may be varied to suit requirements.

Conversion of hydrocarbonbils of relatively high-boiling nature ispreferably carried out with increasing rates of heat input from theinlet to the outlet of tube bank l1, and, in such cases, baflle 22 ispreferably omitted and the quantity of excess air supplied to thefurnace as well as the method by which it is introduced into thecombustion chamber is controlled, as previously described, so as toobtain higher average rates of decreasing rates of heat input towardsthe outlet.

of the coil, the flowof gases under tube bank I1 is either restricted oreliminated byinstallation of a bafiie, such as indicated at 22 in Figure1 of the drawing, inorder to restrict or eliminate the convection heatcomponent which would otherwise be sup lied to tube bank H by thisstream of gases. Also theamount of excess air supplied to the combustionzone and the manner in which it is supplied to this zone may be varied,as previously described-so as to obtain the desired rates of heat inputin various portions of the fluid conduit, suitable for the type of oilundergoing treatment.

Particular attention is directed to the cooperative relation between theuse of a. baffie between the bank of floor tubes and the bridge wall ofthe furnace and the methods,- previously dethe inlet to the outlet ofscribed, for controllingconibustion conditions in the furnace.

It will be apparent from the foregoing that in the present invention ingcurve, regulated to suit the of oil undergoing virtue of the cooperativenature of the arrangement of fluid conduits illustrated and described,the path of flow of the oil therethrough and regulation of the firingconditions as herein disclosed. This is accomplished in the presentinvention without any change in the arrangement of the fluid conduitsfor oils of difierent charac-. teristics and even without .any change inthe direction and path of flow of the oil through the fluid conduit. Itis thus possible, when desired, to change the type of heating curveemployed particular type any desired type of heat- I treatment, isobtainable by even whilethe process is inoperation, which may turned tothe heating coil, the reaction space in i the reaction chamber, whenoperating on a nonresiduum basis, variations or intentional changes inthe character of the charging stock and the like.

I claim as my invention:

1. In a furnace, for the heating of fluids, having side walls, endwalls, a roof and a floor, and a combustion and heating zone, thecombination of'a firing tunnel communicating with said combustion andheating zone, through which a parmixture is tially or completely burnedfuel-air supplied thereto, means for separately introducing regulatedquantities of additional air to the combustion and heating Zone aboveand beneath the firing tunnel, a fluid conduit located adjacent the roofof the furnace, and a fluid conduit located adjacent the floor of thecombustion and heating zone.

2. In a furnace, for the heating of fluids, having side walls, endwalls, a roof and a floor, a combustion and heating zone and a separateheating zone supplied with combustion gases from the combustion andheating zone and separated therefrom by a bridge wall, the combinationof a firing tunnel communicating with said combustion and heating zonethrough which a partially or completely burned fuel-air mixture issupplied thereto, means for separately introducing regulated quantitiesof additional air to the combustion and heating zone above and beneaththe firing tunnel, a fluid conduit located in said separate heatingzone, a fluid conduit located adjacent the roof of the furnace, a fluidconduit located adjacent the floor of the combustion and heating zonebetween the firing tunnel and the bridge wall, means comprising a baiilelocated between the last mentioned fluid conduit and the bridge wall forpreventing the cyclic circulation of combustion gases beneath andthrough said fluid conduit and means for passing a stream of fluid to beheated through the fluid conduit in the order above mentioned.

3. In a furnace, for the heating of fluids, having side walls, endwalls, a roof and a floor, a 1

combustion and heating zone and a separate heating zone supplied withcombustion gases from the combustion and heating zone and separatedtherefrom by a bridge wall, the combination of a firing tunnelcommunicating with said combustion and heating zone through which apartially or completely burned fuel-air mixture is supplied thereto,means for separately intro ducing regulated quantities of additional airto the combustion and heating zone above and be-. neath the firingtunnel, a fluid conduit located in said separate heating zone, a fluidconduit located adjacent the roof of the furnace, a fluid conduitlocated adjacent the floor of the combustion and heating zone betweenthe firing tunnel and the bridge wall, means comprising a bafile locatedbetween the lastmentioned fluid conduit and the bridge wall forrestricting the cyclic circulation of combustion gases about said fluidconduit and meansfor passlng a stream oi fluid to be heated through thefluid conduits in "the order above mentioned.

i. In a furnace, for the heating of fluids, haw ing side walls, endWalls, a roof and a floor, and

a combustion and heating zone, the combination of a firing tunnelcommunicating with said com bustion and heating zone, through which apartially or completely burned fuel-air mixture is,

supplied, thereto, meansv for separately introducing regulatedquantities of additional air to combustion and heating zone abovebeneath the firing tunnel, a fluid conduit located adjacent the roof ofthe turn-ace, a bridge wall, a fluid conduit located adjacent the flooroi the combustion zone between the firing ttumel and the bridge wall,and means comprising a baffle located between the last-mentioned conduitand the bridge wall for preventing cyclic circulation of combustiongases beneath and through said lastmentioned conduit.

5. In a furnace, for the heating of fluids, hav= ing sidewalls, endwalls, a roof and a floor, a combustion and heating zone and a separateheating zone supplied with combustion gases from the combustion andheating zone and separated therefrom by a bridge wall, the combinationof a firing tunnel communicating with said combustion and heating zone,through which a partially or completely burned -air mixture is suppliedthereto, means for separately introducing regulated quantities ofadditional air to the combustion and heating zone above and beneath thefiring tunnel, a fluid conduit located in said separate heating zone, afluid conduit located adjacent the roof of the furnace, a fluid conduitlocated adjacent the floor of the combustion zone between the firingtunnel and the bridge wall, means comprising a bame located between thelast mentioned fluid conduit and the bridge wall for preventing orrestricting the local circulation of combustion gases about said fluidconduit and means for passing the fluid to be heated first through thefluid conduit in said separate heating zone, in a general directioncountercurrent to the general direction of the flow oi the combustiongases through this zone, then through the fluid conduit adjacent theroof of the furnace, in a general direction counter-current to thegeneral direction of the firing, then through the fluid conduit adjacentthe floor oi the combustion zone, in a general direction concurrent tothe direction of firing, and finally out of the furnace.

' 6. in a furnace, for the heating or" fluids, hav ing side walls, endwalls, a roof and a floor, and a combustion and heating zone, thecombination of a firing tunnel communicating with said combustion andheating zone through which a partially or completely burned fuel-airmixture is supplied thereto, means for separately introducing regulatedquantities of additional air to the combustion and heating zone aboveand beneath the firing tunnel, a fluid conduit comprising a singlehorizontal row of horizontally disposed tubular elements locatedadjacent the roof of the furnace, and a fluid conduit comprising asingle horizontal row of horizontally disposed tubular elements locatedadjacent the floor of the furnace.

7. In a furnace, for the heating of fluids, having side walls, endwalls, a roof and a floor, a combustion and heating zone and a separateheating zone supplied with combustion gases from the combustion andheating zone and separated therefrom by a bridge wall, the combinationor" a firing tunnel communicating with said oombustion and heating zonethrough which a par tially or completely burned fuel-air mixture issupplied thereto, means for separately introduc ing regulated quantitiesor" additional air to the combustion and heating zone above and beneaththe firing tunnel, a fluid conduit comprising a plurality oi horizontalrows of horizontally dis posed tubular elements located within saidseparate heating zone, a fluid conduit comprising a single horizontalrow of horizontally disposed tubular elements located adjacent the roofof the furnace, a fluid conduit comprising a single horizontal row ofhorizontally disposed tubular elements located adjacent the floor of thefurnace between the firing tunnel and the bridge wall, means comprisinga baffle located between the last mentioned fluid conduit and the bridgewall for preventing or restricting the local circulation of combustiongases about said fluid conduit, means for passing the fluid to be heatedfirst in series through adjacent tubes in each row of the fluid conduitlocated in said separate heating zone and through the adjacent rows ofthis fluid earn duit in series, in a general direction counter-currentto the general direction of flow of the combustion gases through thiszone, then in series through adjacent tubes in the fiuid conduit locatedadjacent the roof of the furnace, in a general direction counter-currentto the general direction of firing, then in series through adjacenttubes in the fluid conduit located adjacent the floor of the combustionand heating zone, in a general direction concurrent to the generaldirection of firing, and finally out of the furnace.

8. An apparatus for heating fluids comprising a furnace having sidewalls, a roof and a floor, a bridge wall between the side wallsextending upwardly from thefloor and terminating short of the roof,means for firing the furnace adjacent its lower portion through one ofsaid side walls toward the bridge wall, means for introducing air to thefurnace above and below the firing means, a fluid conduit adjacent thefloor between the firing means and the bridge wall in a horizontal planebelow the plane of the firing means, and means comprising a bame locatedbetween said conduit and the bridge wall for preventing cycliccirculation of combustion gases beneath and through the conduit.

9. An apparatus for heating fluids comprising a furnace having sidewalls, a roof and a. floor, a

bridge wall between the sidewalls extending upwardly from the floor andterminating short of 7 firing the furnace adjacent its lower portionthrough one of said side walls toward the bridge wall, means forintroducing air to the furnace above and below the firing means, abaflie of lesser height than the bridge wall extending upwardly fromthe, floor between the bridge wall and the firing means, a fluid conduitadjacent the floor between the firing means and the baflle in ahorizontal plane below the plane of the firing means, a fluid conduit inthe space between the bridge wall and the other of said side walls, anda fluid conduit adjacent the furnace roof having in the space defined bythe bridge wall and the side wall through which the furnace is fired.

10. An apparatus for heating fiuids comprising a furnace having sidewalls, a rodf and a fioor, a firing tunnel projecting through one of theside walls above the floor, means for introducing air to the furnaceabove and below the firing tunnel, heating tubes adjacent the roof ofthe furnace, and additional heating tubes adjacent the floor of thefurnace below the plane of the firing tunnel.

11. An apparatus for ing a furnace having side walls, a roof and afioor, a bridge wall between the side walls extending upwardly from thefloor and terminating short of the roof, means for firing the fur-''nace adiacent its lower portion through one of said side walls towardthe bridge wall, a fiuid conduit adjacent the furnace fioor between thefiring means and the bridge wall, and means comprising a baffle locatedbetween said conduit and the bridge wall for preventing cycliccirculation of combustion gases beneath and through the conduit.

12. An apparatus for heating fluids comprising a furnace having sidewalls, a roof and a fioor, a bridge wall between the side wallsextending upwardly from the floor and terminating short of the roof, afiring tunnel projecting through one of said-side walls into the lowerportion of the furnace, a fluid conduit adjacent the floor below theplane of the firing tunnel and disposed between the last-mentioned-sidewall and the bridge wall, and means comprising a baffle located betweensaid conduit and the bridge wall for restricting local circulation ofcombustion gases about said conduit.

fLEv A.IMEKLER.

at least a portion thereof heating fluids compris-

